1. Field of the Invention
The present invention concerns a method and system for estimating flow rates of fluids from each of separate influx zones in a multilayered reservoir to a production flow in a well in the reservoir.
The method and system may be used for indicating potential crossflow in wells that are draining multilayered reservoirs. The method and system may further be used for estimating influx volumes of fluids from zones in a multilayered reservoir with potential crossflow to a production flow in a well. The fluids may be water, oil, or gas.
2. Description of Related Art
In multilayered reservoirs, the hydrocarbon production flow may be produced from multiple zones having different properties and different backpressures. This results in a situation where the produced hydrocarbons from a zone may flow into the well and out into other zones in the formation, a phenomenon called crossflow. The effect is mostly experienced when wells are shut in and at low flow rates.
A method for monitoring and characterizing multilayered reservoirs is described in SPE 132596 “Best practices in Testing and Analyzing Multilayer Reservoirs” by Pan et al. and is based on testing and analyzing the pressure transient behavior of the multilayer reservoir in combination with the Selective Inflow Performance (SIP) production logging technique (PLT). In this paper, a production logging tool is measuring the flow profile and well hole pressures in the well during various flow rates. The logging tool is lowered down into the well and dragged up and down in the well, providing measurements in different zones in the well during the procedure. This procedure is very expensive and time consuming and the running of a PLT is not always an option due to poor accessibility. The procedure requires the logging tool inside the well, and thus the use of large equipment for handling the tool; e.g., a drilling vessel. There is also the risk of the logging tool getting stuck in the well with the possible result of complete abandonment of the well.